Our capacity to determine intermolecular forces in aqueous or physiological milieux now covers proteins and nucleic acids as well as phospholipid bilayer membranes. There is good evidence that hydration forces dominate interactions near contact. These forces are due to the disturbance of water by charges on the exterior of large molecules or aggregates. Exponentially decaying hydration forces, first characterized quantitatively between bilayer membranes, are typically repulsive. They depend on the chemical identity and packing of water polar soluble groups on the membrane surface. They vanish when an opposing body sticks more strongly to these water soluble groups than does water. Measurements of intermolecular forces in proteins or nucleic acid are now underway using osmotic stress methods developed for membranes. Evidence is strong for the action of hydration forces bewteen parallel DNA double helices. Programs written on the DCRT molecular display system are being developed to examine contacts between proteins in crystals and between nucleic acids in condensed arrays.